Impulse turbine bucket



Jan. 21, 1936. .w. M. WHITE IMPULSE TU1 1BI NE BUCKET Filed May 31; 1954 therefrom. Such redistribution of thematerial- Patented Jan. 21, 1936 UNITED STATES PATENT OFFICE 2,028,369 IMPULSE TURBINE BUCKET William M. White, Milwaukee, Wis. Application May 31, 1934, Serial No. 728,335

9 Claims.

thickness of the walls thereof due to the manuforces involved. Such ribs and lugs however produce such unequal distribution of material in the bucket that difliculties were encountered-in casting and annealing the same. Even with the provision of such ribs, it was also found-that the buckets were destroyed during operation due to' impact stresses setup byimpingementof the jet on the forward portion of the bucket and also due to centrifugal force. It has been found that redistribution of the material in a bucket permits improvement of the efiiciency thereof by allowing a decrease in the angle of discharge of the water also results in improvement during casting and annealing operations on the bucket and in diminishing the wastage due to imperfect workmanship. The distribution of the material also strengthens the bucket at the point where strength is particularly required for the reason that the quantities of material at the locations subject to stresses of any nature are adapted particularly to the stresses encountered.

It is therefore among the objects of the present invention to provide an improved form of bucket for hydraulic turbines of the impulse type in which the inner surfaces or the surfaces of the bucket upon which the jet impinges remain generally in theform of ellipsoids but the outer surfaces thereof deviate from the usual ellipsoidal form.

Another object of thepresent invention is to i provide an improved form of bucket for hydraulic turbines of the impulse type in which the emciency of a bucket of the ellipsoidal form is improved by change in the angle of discharge of the fluid therefrom at the portion thereof most likely to interfere with the following bucket. 5 Another object of the present invention is to provide an improved form of bucket for hydraulic turbines of the impulse type in which the material forming the bucket and its attaching means is substantially uniformly distributed throughout the bucket structure as a whole thereby avoiding manufacturing difiiculties.

Another object of the present inventionis to provide an improved form of bucket for hydraulic turbines of the impulse type in which the material forming the bucket itself is unequally distributed, the greater quantity of material being located at the region of occurrence of the greater stress'and the greater erosion.

Objectsand advantages other than those above set forth will be apparent fromthe following description when read in connection with the accompanying drawing in which:

Fig. 1 is a plan view of the entire structure of an impulse wheel bucket in which the material forming the entire structure is substantially uniformly distributed therethrough and in which the efficiency of the bucket is increased and the bucket is materiallystrengthened at the portions 0' subject to the greatest stress and greatest erosion.

Fig; 2 is a cross sectional view taken on the plane II-II of Figure 1 to illustrate the distribution of the material at the intersection of the ellipsoids forming the divider or splitter for the water jet;

Fig. 3 is a cross-sectional view taken on the plane III-III of Figure 2 to illustrate the varying distribution of the material in the Walls forming the ellipsoids.

Fig. 4 is a partial sectional view of two adjacent buckets taken on the plane OIV of Figure 1 to illustrate the change in the angle of discharge from the bucket at that plane and to illus-- trate the fact that material may be removed from the outer portion of the bucket to'more completely prevent interference of the discharge bucket .wall at that portion thereof Withoutcaus- 55 ing interference with the discharge from following bucket;

Fig. 6 is a partial sectional view of two adjacent buckets on the plane O-VI and illustrating the change in the discharge angle obtained along the plane OVI while permitting the addition of material to the bucket at that portion to strengthen the same; and

Fig. 7 is a partial sectional view of two adjacent buckets taken on the plane OVII and illustrating the changed angle of discharge obtained along such plane while permitting the addition of a greater quantity of material thereto to strengthen the bucket at the location of greater stress thereon.

Referring more particularly to the drawing by characters of reference, reference numerals H and I2 designate a pair of ellipsoids with intersecting surfaces which form a divider or splitter iii in the plane of the axis of the jet (not shown). The ellipsoids, for the purposes of clarity and simplicity in the present description, are divided into lip portions 14 and I5, side portions i1 and I8 and rear portions 2! and 22. The lips l4 and I5 are materially thickened and side portions H and 18 are made with relatively thin upper portions. The rear portions 2| and 22 may also be thickened if desired though such thickening is not essential as will appear hereinafter. The thickening of the lips is continued downwardly and rearwardly along the bottom of the bucket until it merges with the fastening lugs 23 and 24 by which the bucket is to be secured to the rotor disk (not shown). The thickening of the bucket lip also extends laterally in both directions, the adjacent edges merging into each other. Such thickening thus provides for increase in the quantity of' material in the bucket wall across the front of the bucket and extends in the form of enlarged sections or strips along the bottom of the bucket.

The lugs 23 and 24 are joined by a brace 26 extending from between the thickened bottom portions of the bucket at substantially the midpoint thereof to the lower front edges of the lug. Reinforced rear bucket portions are thus formed even though the rear portions 2| and 22 are not thickened as above described with reference to the lips of the bucket.

Thickened portions are thus provided extending across the front of the bucket and extending rearwardly from the front to the portion thereof adjacent the connection with the lug. Such thickened portions are, in a sense, ribs which are located at the points of greatest impact and centrifugal stresses and provide the greatest quantity of material at the locations of greatest corrosion and erosion. Due to the provision of such thickened portions as above described, it is possible to remove material from the outer edges of the bucket and to decrease the angle of discharge therefrom as is illustrated in Figs. 4, 5, 6 and '7 by the amount designated A, B, C, and D. Figs. 4, 5, 6 and 7 also disclose the fact that the regions of greatest interference with the following bucket are the side portions l1 and I8 and that the greatest quantity of material must be removed therefrom to secure the maximum discharge angle for the bucket and hence the greatest efficiency. Such removal of material is possible in the structure herein disclosed because the relatively thin portions of the sides l1 and I8 merge, on three sides, into thickened portions thus providing the required strength. Such side portions now merely constitute water deflecting and guiding means which permit a large decrease in discharge angle of the water thus increasing the efficiency of the bucket.

The bucket when viewed as a whole, has the material more uniformly distributed there'- through. -In manufactu ing, the lip portions are not cut away until the final stages of the manufacturing process are reached. The thickened lips thus provide a mass of material more nearly equal to that of the lugs than was possible heretofore thus avoiding the occurrence of high heat stresses in casting such bucket which stresses were previously unavoidable. Segregation of the various components of the material forming the bucket no longer takes place and waste in the manufacturing process is accordingly reduced.

Considering merely the ellipsoids H and 12, it will be seen that the material forming the same is unequally distributed therethrough, being placed at the locations subject to the greatest forces and to the greatest wear. Such unequal distribution is in fact the reason for both the greater efficiency and the longer life of the bucket.

It will be seen from Figs. 6 and 7 that the discharge water misses the following bucket by a wide margin due to the fact that the buckets are set around the periphery of the rotor disk and are therefore at an angle to each other. Such angularity however affects only the water discharging from the lip portions, and has no infiuence on the water discharging from the side portions of the bucket. The thickness of the side walls must therefore be reduced to avoid discharge interference with the following bucket. Such reduction in thickness is possible in the present construction and causes the large increase in efficiency obtained from the novel buckets disclosed.

Although but one embodiment of the present invention has been illustrated and described it will be apparent to those skilled in the art that various changes and modifications may be made therein without departing from the spirit of the.

invention or from the scope of the appended claims.

.It is claimed and desired to secure by Letters Patent:

1. A bucket for hydraulic turbines of the 1mpulse type comprising intersecting ellipsoids, and lugs extending therefrom, said ellipsoids having thickened lip and bottom portions and reduced thickness side portions whereby the angle of discharge is decreased.

2. A bucket for hydraulic turbines of the impulse type comprising intersecting ellipsoids, and lugs extending therefrom, said ellipsoids having thickened lip and bottom portions and reduced thickness side portions, the thickened and the reduced portions merging into each other and into said lugs to distribute the material forming said ellipsoids dependent on operating stress and wear.

3. A bucket for hydraulic turbines of the impulse type comprising intersecting jet receiving bowls having concave surfaces of substantially ellipsoidal form and having convex surfaces deviating from the ellipsoidal form by addition of material to the lip portions thereof and removal of material from the side portions thereof, and lugs extending from said bowl.

- 4; A bucket for hydraulic turbines of the impulse type comprising intersecting jet receiving bowls having concave surfaces of substantially ellipsoidal form and having convex surfaces, and lugs extending from said bowls, the lip portions of said bowls being thickened downwardly and rearwardly toward said lugs and changing the convex surfaces from ellipsoidal form.

5. A bucket for hydraulic turbines of the impulse type comprising intersecting jet receiving bowls having concave surfaces of substantially ellipsoidal form and having convex surfaces, and lugs extending from said bowls, the lip portions and the bottom portions of said bowls being thickened to provide excess material in the operating stress and wear receiving portions of said bowls.

6. A bucket for hydraulic turbines of the impulse type comprising intersecting jet receiving bowls having concave surfaces of substantially ellipsoidal form and having convex surfaces, and lugs extending from said bowls, the lip portions of said bowls being thickened laterally from the center thereof to provide additional material along the jet entering portion of said bowls.

'7. A bucket for hydraulic turbines of the impulse type comprising intersecting jet receiving bowls having concave surfaces of substantially ellipsoidal form and having convex surfaces, and lugs .extending from said bowls, the lip portions of said bowls being thickened laterally from the major axis through said bowls and the bottom portions of said bowls being thickened parallel with the major axis through said bowls, such thickening providing a mass of material in said bowls substantially equal to the massof material in said lugs to thereby reduce stresses produced during manufacture.

8. A bucket for hydraulic turbines of the impulse type comprising intersecting jet receiving bowls having concave surfaces of substantially ellipsoidal form and having convex surfaces, and

' lugs extending from said bowls, the lip portions and the bottom portions 7 of said bowls being thickened and the side portions of said bowls being reduced in thickness and merging intothe thickened portion.

9. A bucket for hydraulic turbines of the impulse type comprising intersecting jet receiving bowls having concave surfaces of substantially ellipsoidal form and having convex surfaces, and lugs extending from said bowls, the lip portions of said bowls being thickened laterally and longitudinally of the major axis of said bowls and the side of said bowls being reduced in thickness and merging into the thickened portions to distribute the mass of material forming the buckets substantially uniformly throughout the bowls and thereby changing the convex surface from ellipsoidal form.

WILLIAM M. WHITE. 

